Hydraulic measuring mechanisms for registering pressure differences comprise, usually, a measuring mechanism platform having a first pressure input opening and a second pressure input opening, from which, in each case, a hydraulic path extends to a pressure difference measuring cell, in order to supply the pressure difference measuring cell with the first pressure and the second pressure, whose difference is to be measured by the pressure difference measuring cell. A pressure difference measuring cell includes generally a measuring cell platform with two measuring chambers in its interior, which are separated from one another by a measuring diaphragm. The two measuring chambers are, in each case, contactable through a measuring chamber opening with one of the two pressures, so that the measuring diaphragm has an elastic deformation dependent on the difference between the two pressures.
The pressure input openings of the measuring mechanism platform are, usually, sealed by flexible, metal, isolating diaphragms, which, in each case, transfer a pressure presiding on an outside of the isolating diaphragm into the hydraulic path. In the case of measuring mechanisms with coplanar pressure input openings, the pressure inputs lie next to one another on a process connection surface of the measuring mechanism platform. Such measuring mechanisms with coplanar pressure inputs are disclosed, for example, in European Patents, EP 0 370 013 B1, EP 0 560 875 B1, EP 0 774 652 B2, and EP 1 216 404 B1. The hydraulic paths comprise, for example, capillary lines, which extend from a rear side surface of the process connection body, which faces away from the process connection surface, to the pressure measuring cell.
The capillary lines are connected, for example, by an encircling weld seam, pressure-tightly with the measuring mechanism platform and therewith hydraulically coupled, in each case, to one of the pressure input openings.
Providing the encircling weld seams proves, however, to be difficult, since the neighboring capillary tubes get in the way of the circling of the respectively other capillary tube with a welding apparatus.